Stock exchanges BSE and NSE have sought clarification from various listed companies of Tata Group about purported disclosure by Cyrus Mistry about Rs 1.18 lakh crore possible writedown at these firms.

The sacking of Cyrus Mistry from Tata Sons chairman post took a fresh turn of events today with leading stock exchanges BSE and NSE seeking clarification from various listed companies of Tata Group about purported disclosure by the ousted chairman about Rs 1.18 lakh crore (USD 18 billion) possible writedown at these firms.

Markets regulator Sebi has also begun looking into the case for any possible breach of corporate governance norms and listing regulations at various listed companies of the over USD 100 billion conglomerate.

The exchanges have asked these companies, including Tata Motors, Tata Steel, Indian Hotels, Tata Teleservices and Tata Power, to provide full details about these issues.

The notices from the stock exchanges followed reports about Cyrus Mistry, who was ousted as the chairman of the group's main holding company Tata Sons, disclosing possible writedown to the tune of $18 billion faced by the conglomerate.

The exchanges have asked the companies to provide "clarification/confirmation on the news item in detail".

The companies have also been asked to explain "whether such event/negotiations/article stated in published news were taking place?

"If so, you are advised to provide the said information along with the sequence of events in chronological order and the material impact of this article on the company," the exchanges said.

The companies have also been asked about "any information that has not been announced to the exchanges" as required under the Listing Regulations.

The exchanges are also keeping a close watch on the price movement and trading activities of over two dozen listed companies of Tata group, which have seen an erosion in value in last two trading sessions after the surprise ouster of Mistry in less than four years of being made Tata Sons chief.

The price movement and trading volumes for few days prior to the surprise announcement will also be looked into.

The companies were yet to respond to the exchanges.

Markets regulator Sebi is also keeping a close tab on the case.

"We are taking note of each and every development and will act immediately if there is any hint of possible violation of corporate governance and listing norms or any other regulation under our jurisdiction," a senior official said.

"We (Sebi) are taking note of each and every development and will act immediately on any hint of possible violation of corporate governance and listing norms or any other regulation under our jurisdiction," a senior official said.

The Securities and Exchange Board of India (Sebi) is looking into the alleged disclosure made in the purported letter written by Mistry to Tata Sons' board members including about financial and other irregularities as also lapses on the corporate governance front, sources said.

In an explosive confidential email to Tata Sons board members, Mistry warned that the salt-to-software giant may face Rs 1.18 lakh crore in writedowns because of five unprofitable businesses he inherited.

Mistry said he inherited a debt-laden enterprise saddled with losses and went on to single out Indian Hotels Co, passenger-vehicle operations of Tata Motors, European operations of Tata Steel and part of the group's power unit and its telecommunications subsidiary as "legacy hotspots."

As the bitter war played out between him and interim Chairman Ratan Tata, Mistry also alleged that due to the latter's passion for aviation, Tata Sons board increased capital infusion in the aviation sector at multiple levels of the initial commitment.

In a letter written to the Board members of Tata Sons a day after he was ousted, Mistry said: "Board members and trustees are also aware that in the case of Air Asia, ethical concerns have been raised with respect to certain transactions as well as overall prevailing culture within the organisation.

Mistry went on to allege that "executive trustee Mr Venkataraman, who is on the board of Air Asia and also a shareholder in the company, considered these transactions as non-material and did not encourage further study".

It was only at the insistence of the independent directors, one of whom immediately submitted his resignation, that the board decided to belatedly file a first information reports, Mistry said in the letter.

He claimed it was Tata who completed negotiations with Air Asia but early in his tenure as the Chairman of Tata Sons he was asked to table a proposal for the JV with Air Asia at a Tata Sons board meeting.

Claiming that in the case of JV with Air Asia, he was able to extract a "promise of no debt to be raised at the level of JV, as well as limiting Tata Sons investment to 30 per cent of the USD 30 million equity", Mistry said he was taken by surprise with a similar situation when Tatas formed a JV with Singapore Airlines.

"A few months later, I was surprised to be confronted with a similar situation requiring me to execute a fait accompli JV with Singapore Airlines," he said.

Mistry further said in the letter, "without the benefit of time and experience to fully evaluate the proposal, I had to accept that Tata Sons would take a 51 per cent stake in a USD 100 million joint venture".

Pointing fingers at Tata, he said: "The passion for the airlines sector has led Mr Tata to continue his involvement with strategy of the two airlines. It is on his advice that the Tata Sons board has increased the capital infusion in the sector at multiple levels of the initial commitment."

In 2013, Tata Sons had joined hands with Malaysian carrier AirAsia and Arun Bhatia's Telestra Tradeplace to start low cost carrier AirAsia India. The carrier had to wait for nine months before taking off.

In September 2013, Tata group had joined hands with Singapore Airlines to start a new full-service airline in India, 18 years after a failed attempt. Tata Sons owned 51 per cent stake in the carrier, which has been christened asm Vistara with Singapore Airlines holding the rest.